Chola Gangam: The Forgotten Reservoir of Tamil Nadu – A Civilisational Marvel in Ruins

 

Chola Gangam: The Forgotten Reservoir of Tamil Nadu – A Civilisational Marvel in Ruins

By Suryavanshi IAS

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Introduction

In the heart of Tamil Nadu, a forgotten marvel of Chola hydraulic engineering lies in disrepair—Chola Gangam, also known locally as Ponneri Lake, a 17-kilometre-long tank built by Rajendra Chola I to commemorate his victorious northern expedition and water management mastery. As India moves forward with infrastructure growth, the tale of this thousand-year-old tank calls for introspection into ancient wisdom, sustainable water governance, and cultural heritage conservation.

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Historical Background

• Builder: Rajendra Chola I (son of Rajaraja Chola I), early 11th century CE.

• Purpose: A ganga-jalamayam jayastambham or “liquid pillar of victory” to mark his victorious Ganges expedition (c. 1019 CE).

• Mentioned In: Tiruvalangadu Copper Plates, The Cholas by K.A. Nilakanta Sastri.

• Historical Utility:

  • Supplied drinking water to Gangaikonda Cholapuram, the Chola capital.

  • Irrigated nearly 1,564 acres of agricultural land.

  • Supported a 60-acre palace and surrounding settlements.

  • Hosted migratory birds en route to Kodiakkarai Bird Sanctuary.

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Engineering Brilliance

• Length: Originally 16 miles (~25.7 km); now only 17 km remains.

• Bunds: Built in an elliptical shape using laterite stones to resist hydraulic pressure.

• Sluices: Designed to trap silt, now mostly defunct except one.

• Sediment Trap System:

  • Designed to carry nutrient-rich silt into paddy fields.

  • Supported by ‘thoompu’, a vortex flow outlet.

  • Traditional maintenance via ‘kudimaramathu’ and ‘eri-ayam’ tax from farmers.

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Present State of Decline

• Dry and Shrinking: Relies on rainwater, with feeder canals from the Kollidam River abandoned.

• Encroachment: A British-era bridge now runs through the dry lakebed.

• Ecological Impact:

  • Migratory birds no longer stop.

  • Groundwater depletion: Water table down to 650 feet.

• Lack of Restoration: Despite a 170-year-old British-era proposal to revive the tank, no significant action has been taken.

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Relevance Today

1. Groundwater Recharge and Water Security

• The tank, if linked again to Kollidam and restored, could:

  • Revive 12 ancient lakes in the northern Cauvery delta.

  • Recharge groundwater in Gangaikonda Cholapuram.

  • Supply water to cities like Chennai, especially during droughts.

2. Agricultural Fertility

• Restoration can enhance fertility of thousands of acres in Tiruchi and South Arcot districts.

• Acts as a drainage outlet for the Veeranam Lake, strengthening the tank network.

3. Heritage Conservation

• Reflects India's civilisational engineering and water wisdom.

• Can be declared a protected monument under the ASI or State Heritage Act.

• Preservation supports cultural tourism and local livelihoods.

4. Ecological Balance

• Restoring the tank could revive bird migration paths, contributing to biodiversity.

• Offers a natural flood buffer during intense monsoons.

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Way Forward / Recommendations

Issue	Solution
Drying tank & collapsed canal network	Re-link with Kollidam River using modern hydrology and traditional maps.
Ecological loss	Rewilding and conservation of migratory bird routes.
Lack of awareness	Commemorative coin, PM visit, public campaigns to raise visibility.
Lack of policy attention	Include in Smart Cities Mission, Amrit Sarovar Yojana, or State Heritage Projects.
Engineering gap	Employ PWD engineers, consult hydraulic historians, and revive 'kudimaramathu' participatory practices.

UPSC Relevance: Multidimensional Learning

Paper	Topic Link
GS I	Indian History – Rajendra Chola, ancient engineering, cultural heritage.
GS II	Governance – Heritage policy, local administration (tank tax, kudimaramathu).
GS III	Environment – Water conservation, sustainable irrigation, ecology.
Essay	“Water as Culture: Past Traditions and Present Crisis” or “Learning from Ancient India’s Infrastructure”
Ethics (GS IV)	Accountability, stewardship of natural and cultural resources.

Conclusion

The story of Chola Gangam is not just about a forgotten lake. It is a symbol of India’s ancient genius, now at the mercy of apathy. A revival of such marvels could lead to a sustainable, inclusive, and heritage-conscious model of development that India urgently needs today. As Prime Minister Modi’s visit nears, it is hoped this neglected “liquid pillar of victory” will receive the dignity it deserves.

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Mind Map: Chola Gangam – A Civilisational Reservoir

                                 [Chola Gangam Tank]
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  [Historical Significance] [Engineering Marvel]  [Present State] [Way Forward]
        |                      |                       |              |
 Rajendra Chola I     Elliptical bunds, sluices   Dry, encroached   Link to Kollidam
  Ganga expedition     Laterite stone strength    Wildlife loss     Declare heritage
  Tiruvalangadu plates  Sediment ejection system  Groundwater drop  Include in missions